AB0568 CHRITHIDIA LUCILAE IMMUNOFLUORESCENCE PRESENCE IN SYSTEMIC LUPUS ERYTHEMATOSUS AND ITS ASSOCIATION WITH POSITIVE CHAGAS TESTS
Authors: E. Picco, B. Cañizares, R. Rojas Tessel, E. Buschiazzo, M. Aciar, N. Cucchiaro, L. N. Belbruno, M. B. Lecumberri, A. C. Ralle, V. Juarez, M. E. Crespo Espindola
Journal: Annals of the Rheumatic Diseases (2022)

Background Systemic lupus erythematosus (SLE) is characterized by the presence of auto-antibodies, including anti-double strained DNA (dsDNA), which are highly specific for the disease diagnosis and its follow up. Indirect immunofluorescence (IIF) using chritidia luciliae (CL) as the antigenic substratum, is the most widely used method to detect it, and its positivity is defined with the staining of the kinetoplast and/or the nucleus. CL is a flagellated parasite, included in trypanosomatidae family, which also includes trypanosoma cruzi , the cause of Chagas Disease (CD). Some studies suggest that membrane and flagellum fluorescence (considered ‘atypical’ staining) could be related with positive CD serology. Objectives Describe the prevalence of positive IIF-CL images and its association with positive CD test in SLE patients. Methods A cross sectional study was designed including consecutive outpatients with SLE diagnosis (SLICC criteria), in which anti-dsDNA antibodies was requested to monitor disease activity. At the same time, two serologic CD tests were performed, since they improve sensibility to detect the disease. Anti-dsDNA by IIF were performed by an experienced laboratory biochemistry blinded to patients clinical data. Pregnant patients and those ≤ 18 years old were excluded from this analysis. Standard descriptive analysis was performed, data was compared by exact fisher test or chi2, student’s T test or Mann Whitney. A p value &lt; 0.05 was considered as significative. Results Thirty five patients were included, 33 (94.3) female, median age 38 (IQR 31-48), with 20 (57.1) patients being from middle-low socioeconomic status (measured by Graffar score). Twenty-six (74.3) patients were receiving glucocorticoids, 28 (80) hydroxychloroquine, 5 (14.3) azathioprine, 12 (34.3) mofetil mycophenolate, 5 (14.3) cyclophosphamide and 4 (11.4) rituximab. Twelve (34.4) had positive anti-dsDNA test, with atypical staining in membrane and flagellum 31 (88.9), only membrane 4 (11.4) and 9 (25.7) only basal body. One patient had previous chronic CD diganosis without specific treatment. Five (14.3) CD serologies were positive, and 1 had undefined result. This group of patients had positive staining in membrane and flagellum of CL. No other atypical CL staining images were found. (Table 1) Table 1. CL staining in CD positive v negative serology Chritidia luciliae Structure CD negative (n = 29) CD positive (n = 5) p value Membrane and flagellum – n (%) 25 (86.2) 5 (100) 0.51 Only Membrane – n (%) 4 (13.8) 0 0.51 Basal body – n (%) 7 (24.1) 1 (20)* 0.66 * undefined result Conclusion Although we could not find a statistical association between atypical CL staining and positive CD serology, this could be due to the low number of patients included in the study since all the patients with positive CD serology had a positive staining in CL-IIF. A trained biochemistry operator is necessary to avoid false positive tests in regions with high prevalence of CD. Disclosure of Interests None declared